SFTPD and idiopathic pulmonary fibrosis: Previous studies reported that the standardized uptake value (SUV), a semi-quantitative index for FDG uptake in PET/CT, was associated with lung function, levels of C-reactive protein [CRP], LDH, SP-D, and KL-6, and clinical outcomes (decline in lung function, transplant-free survival, and death) in IPF patients [15–18].